JPH07898B2 - Reinforcement method of corrosion-deteriorated part of steel pipe pile - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of reinforcing a corrosion-deteriorated portion of a steel pipe pile that supports a harbor structure such as a jetty or a dolphin.

<Prior Art> The prior art will be described with reference to FIGS. Steel pipe piles 1 installed in the sea, such as the foundation of a jetty, are tidal zones where the supply of seawater and air is sufficient due to seawater splashes and tides.
At 14, the outer surface of the steel pipe pile 1 corrodes rapidly. In the figure, LWL shows low tide and HWL shows high tide. If the wall thickness of the steel pipe pile 1 is reduced by this corrosion, the cross-sectional area and the second moment of area of the steel pipe pile are reduced, and the stress of the steel pipe pile 1 subjected to the vertical load and horizontal load transmitted from the upper structure increases. When the corrosion progresses and the stress of the steel pipe pile 1 exceeds the allowable stress of the material forming the steel pipe pile 1, the supporting force of the steel pipe pile 1 against the load becomes insufficient, so that the supporting strength of the structure is satisfied. Therefore, it becomes necessary to reinforce the corrosion deterioration part.

Such a problem of corrosion of the steel pipe pile 1 has been rapidly exposed in recent years, and many reinforcing methods have been developed for the steel pipe pile 1 having almost no remaining wall thickness.

Figures 6 and 7 show a typical example of the conventional reinforcement method described in the publication "Port Structure Repair Manual".

Fig. 6 shows an example in which the outer circumference of the steel pipe pile 1 is reinforced with reinforced concrete.
15 is installed, a reinforcing bar 16 is assembled on the head of the stud dowel 15, and a formwork is provided to pour concrete 17.

In FIG. 7, a reinforcing steel plate 18 is attached to the outer periphery of the steel pipe pile 1 by welding to reinforce it.

The stress transmission mechanism thus reinforced will be described with reference to FIG. The stress 20 of the existing steel pipe pile transmitted from the superstructure is transmitted to the reinforcing member on the outer circumference of the existing steel pipe pile through the stud dowel 15, the reinforcing bar 16 or the welded portion 19 shown in FIG. It is transmitted again to the existing steel pipe pile below. In this case, the load bearing capacity of the corrosion-deteriorated portion 2 of the steel pipe pile is not expected at all. Such a construction method has been developed to deal with the corrosion problem which has been suddenly exposed in recent years. That is, as a result of the first corrosion investigation, a pile with almost no remaining wall thickness was discovered, and this is a reinforcement method in a case where it is urgently necessary to reinforce the pile with a required load-bearing capacity.

However, as the corrosion problem has become more serious, more detailed corrosion investigations have been carried out, and the number of cases in which the corrosion state has been confirmed before the above-mentioned residual proof strength can hardly be expected and reinforcement measures can be taken early is increasing. It's starting.

<Problems to be Solved by the Invention> The above-mentioned conventional reinforcement methods that have been developed so far are as follows: (1) In the method shown in FIG. 6, the welding work and the form work of the stud dowel 15 and the reinforcing bar 16 are performed underwater. Because it will be work,
The reliability of the strength of the weld is low and the work efficiency is poor. In addition, the stud dowel 15, the reinforcing bar 16 material and the construction cost are large, which is not economical.

(2) Also in the case of the method shown in FIG. 7, since the welding work of the welding portion of the reinforcing plate is an underwater operation, the reliability of the quality of the welding portion 19 is low, the work efficiency is poor, and the welding length is long, It has the drawback of being expensive.

(3) Further, the method shown in FIG. 7 has a problem that seawater penetrates from the welded portion and corrosion progresses from the inside unless the steel pipe pile 1 and the reinforcing steel plate 18 are completely sealed at the welded portion. Further, the resin coating near the welded portion under the reinforcing steel plate 18 becomes underwater coating, which causes a problem in durability.

It is an object of the present invention to provide a method for reinforcing a corrosion-deteriorated portion of a steel pipe pile, which improves reliability of quality of a joint by minimizing underwater work, and has excellent work efficiency and economy. Is.

<Means for Solving Problems> The present invention solves the above problems, and employs the following technical means in a method of reinforcing a corrosion-deteriorated portion of a steel pipe pile supporting a harbor structure.

a) An upper rib and a lower rib are welded to the upper and lower positions of the corrosion-deteriorated portion of the steel pipe pile over the entire surface of the steel pipe pile, and flanges are attached to the surface of the steel pipe pile further below the lower rib.

b) With a diameter larger than the steel pipe pile above the water surface,
Half-divided steel pipes, each having one or two rows of circumferential ribs provided on the inner surfaces at positions corresponding to the upper ribs and the lower ribs, are welded on the half-divided surfaces to form a mantle tube surrounding the steel pipe pile.

c) Lower this outer tube to cover the corrosion-deteriorated area,
The lower end is placed on the flange.

d) Then, mortar or concrete is filled in the space formed between the steel pipe pile and the jacket pipe.

<Operation> FIG. 2 shows a stress transmission mechanism in a steel pipe pile reinforced by the reinforcing method of the present invention, and FIG. 2 (a) shows a case where compressive stress acts on the steel pipe pile. b) shows the case where tensile stress acts on the steel pipe pile.

In the case of FIG. 2 (a), two rows of upper ribs 6 a and 6 b and lower ribs 7 a and 7 b in the circumferential direction provided on the inner surface of the outer tube 3 are welded over the entire circumference of the surface of the steel pipe pile 1. They are arranged in a zigzag shape in cross section so as to be positioned above and below with the upper rib 4 and the lower rib 5 sandwiched therebetween. The compressive stress 12 acting on the steel pipe pile 1 is transmitted from the upper rib 4 of the steel pipe pile 1 through the concrete or mortar 8 to the outer pipe 3 via the upper lower rib 6b of the outer pipe 3 as shown by the arrow, and then again to the outer pipe. It is transmitted to the steel pipe pile 1 from the lower upper rib 7a of 3 through the concrete or mortar 8 and the lower rib 5 of the steel pipe pile 1. Further, in FIG. 2 (b), the tensile stress 13 acting on the steel pipe pile 1 passes from the lower rib 5 of the steel pipe pile 1 through the concrete or mortar 8 to the lower rib 7b of the mantle tube 3 as shown by the arrow. Is transmitted to the outer tube 3 and is again transmitted to the outer tube 3.
Is transmitted to the steel pipe pile 1 through the upper ribs 4a of the steel pipe pile 1 through the concrete or mortar 8.

Here, when only the compressive stress 12 acts, the upper upper rib 6a and the lower lower rib 7b can be omitted. When only the tensile stress 13 acts, the upper upper rib 6b and the lower upper rib 7a can be omitted. Also, the mantle tube 3
It is necessary that the second moment of area and the sectional area of the steel pipe pile are larger than those of the steel pipe pile 1.

<Example> FIGS. 1 (a), (b), and (c) show an example of the method of the present invention. First, as shown in FIG. 1 (a), upper ribs 4 and lower ribs 5 are welded above and below the corrosion-deteriorated portion 2 of the steel pipe pile 1, respectively, and at the bottom of the reinforcing member mounting position, the outer tube 3 is attached. Attach the flange 9 for mounting. The flange 9 may be of any structure as long as it has a flange height sufficient to mount the outer tube 3 and a supporting force for supporting the weight of the outer tube 3 and the reinforcing material made of concrete or mortar.

Next, as shown in FIG. 1 (b), two half rows of upper ribs 6a, 6b and lower ribs 7a, 7b are welded to the upper and lower ends of the inner surface in advance, and As shown in FIG. 1 (c), the outer tube 3 which is a reinforcing material is manufactured by welding and joining in the vertical direction above the water surface.

Then, as shown in FIG. 1 (d), the outer tube 3 is placed on the upper surface of the flange 9 with the centers of the steel pipe pile 1 and the outer tube 3 aligned,
Concrete or mortar 8 is poured into the space formed between the steel pipe pile 1 and the jacket pipe 3, and the steel pipe pile 1 and the jacket pipe 3
And concrete or mortar 8 are integrated.
Upper and lower ribs 4, which are welded to the steel pipe pile 1 and the jacket pipe 3,
5,6a, 6b, 7a, 7b need only have a pressure-receiving area that receives the bearing pressure of concrete or mortar, and the weld length of the weld has a weld length that ensures the necessary strength. I'm good.

3 and 4 show examples of the shapes of ribs welded to the inner surface of the outer tube 3, FIG. 3 is a band-shaped rib, FIG. 4 is a plate-shaped rib, and the welded portion is indicated by 11. . Fig. 3
The rib of FIG. 4 is similarly applied to the rib of the steel pipe pile 1.

Next, the construction method of the present invention will be described more specifically with reference to FIG. FIG. 5 is a cross-sectional view showing a reinforced portion by this construction method. Upper and lower ribs 4, 5 of steel pipe pile 1 and jacket pipe 3,
It is suitable that the thickness t of 6a, 6b, 7a, 7b is 9 mm or more so that the bearing pressure of concrete or mortar is sufficient, and the width w of the rib is 25 mm or more so that the rib is sufficiently fixed. Also, the gap d between the ribs is set to 50 mm or more so that concrete or mortar can be smoothly filled. It is recommended to use the same dimension as d so that is about 45 °.

The length 1 of the stress transmitting portions above and below the corrosion-deteriorated portion may be equal to or greater than the outer diameter D of the steel pipe pile. By using a heavy-duty food material such as polyethylene-coated steel pipe for the outer pipe, the corrosion prevention of the reinforcing portion can be achieved more effectively. Although the example of welding the rib to the inner surface of the outer tube has been described above, the same effect can be obtained by using an outer tube using a striped steel plate instead of this.

<Effects of the Invention> The construction method of the present invention has the following excellent effects.

Underwater work is only welding the lower ribs of the steel pipe pile and attaching the flanges, and the rest is performed above the water surface, improving work efficiency.

The welding of the upper and lower ribs to the inner surface of the mantle tube and the welding of the joint of the half steel pipe are performed in the atmosphere, so that the quality of the welded portion is guaranteed.

Since concrete or mortar is filled between the steel pipe pile and the reinforced jacket pipe, there is no cavity and no corrosion of seawater.

Anticorrosion coating of reinforced steel plates (including welded parts) can be applied on the water surface, improving construction quality and reducing construction costs.

Since members such as reinforcing bars, stud dowels, reinforcing plates, etc. and their underwater welding are not required, the construction cost is lower than that of the conventional method shown in Fig. 5 or 6, and it is reliable and economical. is there.

[Brief description of drawings]

1 to 5 show one embodiment of the method of the present invention, FIG. 1 is an explanatory view showing the procedure of the method, FIG. 2 is an explanatory view showing the state of stress transmission acting on a steel pipe pile, and FIG. FIG. 4 and FIG. 4 are perspective views showing examples of ribs welded to the outer tube used in the method of the present invention, and FIG. 5 is an explanatory view for specific dimension examples,
6 and 7 are perspective views showing a conventional example, and FIG. 8 is an explanatory diagram of stress transmission by a conventional method. 1 ... Steel pipe pile, 2 ... Corrosion-deteriorated part, 3 ... Mantle tube, 4 ...
… Upper rib of steel pipe pile, 5 …… Lower rib of steel pipe pile, 6a ……
Upper upper rib of outer tube, 6b …… Upper lower rib of outer tube,
7a …… Lower upper rib of outer tube, 7b …… Lower lower rib of outer tube, 8 …… Concrete or mortar, 9 …… Flange

Claims (2)

[Claims] 1. A method of reinforcing a corrosion-deteriorated portion of a steel pipe pile for supporting a harbor structure, comprising: an upper rib and a lower rib at the upper and lower ends of the corrosion-deteriorated portion of the steel pipe pile over the entire circumference of the surface of the steel pipe pile. And a flange is attached to the surface of the steel pipe pile below the lower rib, while the diameter is larger than that of the steel pipe pile above the water surface, and 1 is provided at a position corresponding to the upper rib and the lower rib on the inner surface, respectively. Two or two rows of half-divided steel pipes provided with circumferential ribs are welded on the half-divided surface to form a mantle tube surrounding the steel pipe pile, and the mantle pipe is lowered and its lower end is placed on the flange. A method of reinforcing a corrosion-deteriorated portion of a steel pipe pile, characterized in that the space formed between the steel pipe pile and the jacket pipe is filled with mortar or concrete. 2. An upper rib and a lower rib, wherein two upper and lower circumferential ribs provided on the inner surface of the half-split steel pipe are welded over the entire circumference of the steel pipe pile in a state of being placed on a flange. The method for reinforcing a corrosion-deteriorated portion of a steel pipe pile according to claim 1, wherein the reinforcing pipes are arranged in a zigzag shape in cross section so as to be located above and below.